Integrated circuit with additional mini-pads connected by an under-bump metallization and method for production thereof

ABSTRACT

A semiconductor device includes a semiconductor chip. External connection pads and further pads are disposed over a surface of the semiconductor chip. Selected ones of the further pads are electrically connected to one another so as to activate selected functions within the semiconductor chip.

This application is a continuation of International Application No. PCT/DE2004/002284, filed Oct. 14, 2004, which designated the United States and was not published in English, and which is based on German Application No. 103 49 749.8 filed Oct. 23, 2003, both of which applications are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to an antifuse connection for integrated circuits for the activation of redundant circuits or chip functions of flip-chip arrangements with an under-bump metallization on standard pads on the surface of a chip for the incorporation of bumps, and to a method for production of such antifuse connections.

BACKGROUND

Redundant circuits are usually concomitantly integrated in integrated circuits in order to be able to activate these as required. Such redundant circuits are activated if individual circuit parts are not functional on account of a defective processing (e.g., defects, particles). The redundant circuits then undertake the task of the defective circuits and the overall chip is fully functional.

In order to activate the redundant circuit, the integrated circuit has to be electrically isolated from the defective region and be connected to a redundant circuit (replacement circuit). This is done by means of fuses for isolating current paths and antifuses for connecting current paths.

An example of a fuse and an antifuse and also a method for production and activation of a fuse and an antifuse emerge from German patent application 196 04 776 A1 and corresponding PCT application WO 97/29515.

These fuses have hitherto been integrated in the metallization layers of the integrated circuit. In order to isolate a fuse, then, a laser beam is directed onto it and the fuse is blown. What is problematic in this case is that the fuse is encapsulated in a dielectric, so that the encapsulating dielectric layer often bursts open during the fuse blowing operation. This then results in reliability problems such as leakage currents, corrosion, etc.

After the processing of the chips has finished, the chips are electrically checked for functionality prior to mounting into a housing. Non-functioning chips are repaired with the fuses as above before they are mounted into housings.

SUMMARY OF THE INVENTION

The invention is based on the object, then, of providing an antifuse connection for integrated circuits for the activation of redundant circuits, which can be provided with little outlay and in the case of which the problems that can be noted in the prior art do not occur. Furthermore, the intention is to demonstrate a method by which such antifuse connections can be produced.

The object on which the invention is based is achieved by virtue of the fact that further mini-pads are arranged on the surface of the chip alongside the standard pads. The further mini-pads are electrically connected to functional units in the chip. Selected mini-pads are connected to one another by antifuse connections patterned from the under-bump metallization.

Reliability problems are thus avoided because the antifuses are produced by normal patterning of the UBM metallization and a high-energy laser processing is unnecessary.

The object on which the invention is based is furthermore achieved by means of a method for production of antifuse connections, that is characterized in that firstly the UBM metallization is deposited on the chip and a photoresist layer is deposited on the metallization and the regions of the standard pads are exposed. Subsequently, the areas required for the antifuse connections are additionally exposed by means of a laser or an electron beam. Afterward, the photoresist is developed and the UBM metallization including the antifuse connections is patterned.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below using an exemplary embodiment. In the associated figures of the drawing:

FIG. 1 shows a finished processed chip with standard pads and additional mini-pads for UBM (anti) fuses; and

FIG. 2 shows the finished processed chip according to FIG. 1, after the application and patterning of the UBM metallization and with additional UBM antifuse connections.

The following list of reference symbols can be used in conjunction with the figures:

-   -   1 Standard pad     -   2 Chip     -   3 UBM metallization     -   4 Mini-pad     -   5 Antifuse connection

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the case of the invention described below, a metallization plane, which is used for the application of so-called bumps onto the standard pads 1 on a chip 2 of a flip-chip metallization (UBM: under-bump metallization), is utilized for the formation of fuses or antifuses. After the processing of the wafer has finished, this UBM metallization 3 is deposited in planar fashion on the wafer and, as a result of a subsequent patterning, is left only above the standard pads 1. In a further step, bumps (not illustrated) are then applied to the standard pads 1, by means of which bumps the chip 2 can then be electrically contact-connected to a leadframe or a printed circuit board.

According to FIG. 1, additional mini-pads 4 are provided, which have been led over the product to the top side of the chip 2. The UBM metallization layer can thus be utilized for producing electrically conductive antifuse connections 5 between the mini-pads 4. In this case, selected mini-pads 4 are short-circuited by the antifuse connections 5 (FIG. 2).

The particular advantage of this “antifusing” can be seen in the fact that it is possible to correct the circuit up to directly prior to the packaging of the circuit, that is to say the mounting of the chip 2 on a leadframe and subsequent molding (encapsulation), that is to say up to the concluding UBM deposition and patterning.

A further advantage lies in the fact that the “antifusing” according to the invention cannot lead to any reliability problems whatsoever in the chip 2 since the antifuse connections 5 are situated on the surface of the chip 2 and are only deposited at the required locations.

Furthermore, in contrast to the laser fuses used hitherto, active or passive components can also be arranged under the antifuse connections 5.

The UBM metallization can be used according to the invention for the antifuse connections 5 described and also for programming the circuit. That is to say, the function of the chip can be defined in terms of hardware here in the case of chips with a plurality of functions outside the production line. Furthermore, the UBM metallization can be used as a chip wiring plane, as a result of which a metallization plane can be obviated, which leads to a significant saving of costs.

Before the patterning of the UBM metallization is performed, all the chips 2 on a wafer are tested with regard to their functionality. Afterward, the UBM metallization is deposited and a photoresist layer is deposited thereon and the regions of the standard pads 1 are exposed, but are not yet developed. Afterward, the areas required for the antifuse connections 5 are then additionally exposed for example by means of a laser or an electron beam. Afterward, the photoresist is then developed and the UBM metallization is patterned. This is then followed by the further processes required for flip-chip mounting. 

1. A method of making a semiconductor device, the method comprising: forming an integrated circuit chip; forming an under-bump metallization layer over an upper surface of the chip; forming a photoresist over the under-bump metallization layer; patterning the photoresist to define areas of the under-bump metallization layer located over external connection pads and to define regions of the under-bump metallization layer for antifuse connections; and using the photoresist as a mask, forming the areas and the regions for antifuse connections in the under-bump metallization layer; wherein the antifuse connections electrically connects further pads on a top surface of the chip.
 2. The method of claim 1, wherein patterning the photoresist comprises using a mask to form a pattern for the areas, and, in a separate process step, forming a pattern for the antifuse connections.
 3. The method of claim 2, wherein the separate process step utilizes a laser or an electron beam.
 4. The method of claim 2, further comprising electrically testing the integrated circuit chip, wherein the pattern for the antifuse connections is determined based upon the testing.
 5. The method of claim 2, wherein the pattern for the antifuse connections is determined based upon a desired functionality of the integrated circuit chip.
 6. The method of claim 1, further comprising forming the external connection pads and the further pads, wherein one antifuse connection comprises an electrical connection between a first further pad and a second further pad.
 7. The method of claim 6, wherein the further pads are smaller than the external connection pads.
 8. The method of claim 6, further comprising forming solder bumps over the external connection pads.
 9. A method of making a semiconductor device, the method comprising: providing a semiconductor chip; forming external connection pads over a surface of the semiconductor chip; forming further pads over the surface of the semiconductor chip, selected ones of the further pads being electrically connected over the surface to one another so as to activate selected functions within the semiconductor chip; and forming solder bumps over the external connection pads but not over the further pads.
 10. The method of claim 9, wherein forming the further pads comprises forming further pads that are electrically connected to one another by antifuses.
 11. The method of claim 10, wherein the antifuses are formed in an under-bump metallization layer.
 12. The method of claim 10, wherein providing a semiconductor chip comprises fabricating a semiconductor chip with active circuitry.
 13. The method of claim 9, wherein the external connections pads are arranged alongside opposite edges of the semiconductor chip and wherein the further pads are arranged in a central portion of the chip between the external connection pads.
 14. The method of claim 13, wherein the further pads are smaller than the external connection pads.
 15. A method of making a semiconductor device, the method comprising: fabricating a semiconductor chip; forming external connection pads over a surface of the semiconductor chip; and forming a plurality of disscrete antifuses over the surface of the semiconductor chip at the same time that the external connection pads are formed.
 16. The method of claim 15, further comprising programming the antifuses so as to activate selected functions within the semiconductor chip.
 17. The method of claim 16, wherein programming the antifuses comprises activating redundant circuits.
 18. The method of claim 15, further comprising programming the antifuses to couple together selected circuits within the semiconductor chip.
 19. The method of claim 15, wherein the external connection pads are formed in an under-bump metallization layer and wherein the antifuses are also formed in the under-bump metallization layer.
 20. A method of making a semiconductor device, the method comprising: providing a semiconductor chip; forming external connection pads over a surface of the semiconductor chip; and forming further pads over the surface of the semiconductor chip, selected ones of the further pads being electrically connected over the surface by antifuses to one another so as to activate selected functions within the semiconductor chip, wherein the antifuses are formed in an under-bump metallization layer.
 21. The method of claim 20, wherein providing a semiconductor chip comprises fabricating a semiconductor chip with active circuitry.
 22. The method of claim 20, further comprising forming solder bumps over the external connection pads but not over the further pads.
 23. The method of claim 20, wherein the external connections pads are arranged alongside opposite edges of the semiconductor chip and wherein the further pads are arranged in a central portion of the chip between the external connection pads.
 24. The method of claim 23, wherein the further pads are smaller than the external connection pads. 